The present invention is directed to an optical star coupler for multi-mode light conducting fibers wherein two groups of light conducting fibers are connected to one another by a mixing element. In the coupler, a packing density of each group of fibers at the input and the output of the mixing element is to be as great as possible.
A coupler which has at least an input and output group of fibers interconnected by a mixing element is known and an example is disclosed in an article by Marshall C. Hudson et al, "The Star Coupler: A Unique Interconnection Component for Multimode Optical Waveguide Communication Systems", Applied Optics, Vol. 13, No. 11, November 1974, pp. 2540-2545. These types of couplers are of a great significance in optical communication technology. They contain fibers, which run towards a common nodal point and from which an equal number of fibers re-emerge. The light from an incoming fiber is to be distributed between all of the outgoing fibers as uniformly as possible and with the least possible losses. In particular, when a large number of terminals are to be supplied, the use of star couplers results in smaller overall losses than in a T-shaped arrangement, which is also well known. Consequently, the dynamic range on the receiver side can be contrived to be smaller. In addition, the star-shaped arrangement is more resistant to total breakdown. In the known three dimensional star coupler, an increasing number of fibers result in an increasing technical outlay in order to obtain a high packing density of the fibers in the mixing element. At the same time, it must be ensured that each fiber is aligned and parallel to the axis of the rod-shaped mixing element. On account of these technical requirements, known star couplers, which are used in practice, will exhibit insertion losses which considerably exceed the theoretical values.